1. Field of the Invention
The present invention relates to an apparatus for manufacturing deionized water and using method thereof and; more particularly, to an apparatus and method having a reverse osmotic vessel for manufacturing deionized water.
2. Description of the Related Art
In fabricating highly integrated semiconductor devices, any contamination materials such as particles remaining on semiconductor substrates after cleaning, electrostatic discharge, and water marks, etc. exert an undesirable influence on subsequent process steps and adversely affect device yield. Generally, semiconductor devices are cleaned during fabrication by a wet cleaning process or wet etching process to remove contaminants from semiconductor substrates. For the cleaning process, pure deionized water is used with various chemicals. If deionized water is unpure, the semiconductor substrates may not be properly cleaned. Therefore, a need exists for the production of pure deionized water.
Generally, deionized water is manufactured by using a reverse osmotic pressure method. The reverse osmotic pressure method separates solution having concentration differences to a higher ion solution and a lower ion solution using an apparatus having a reverse osmotic pressure membrane. The higher ion solution is pressurized over the osmotic pressure to transfer water in the higher ion solution to the lower ion solution, and then, the higher ion solution is concentrated with ions and the lower ion solution becomes deionized water. One characteristic of the reverse osmotic pressure method is to purify ions under 1 nm.
An important unit for manufacturing ionized water by using the reverse osmotic pressure method is a reverse osmotic membrane. The reverse osmotic membrane is not durable, thereby deteriorating quality of the deionized water when it is used for a long period. Therefore, the reverse osmotic membrane should be changed by periodically evaluating the membrane performance.
The evaluation of the membrane performance is performed by using a filtering experimental apparatus. The filtering experimental apparatus evaluates a minimum performance by supplying a small amount of water. That is, the membrane is not evaluated in-situ for manufacturing the deionized water, but evaluated by an indirect method. Thus the evaluation substantially depends on operator's skill and may not be correct. Furthermore, in case that a quality of the deionized water is poor, it is difficult to find whether the membrane is poor or the supplied raw water is poor. As a result, if the quality of deionized water is poor, the reliability of semiconductor devices using the deionized water is suffers, thereby lowering yield and productivity of the semiconductor devices.
Therefore, it is highly desirable to design an apparatus and a method for manufacturing deionized water, which has a filtering experimental unit thereof.